The present invention relates to solar collectors and particularly to those including an absorber of solar radiations for heating a heat-exchange liquid.
The known form of solar collector to which the present invention is most related includes a housing containing a darkened heat-absorbing backing plate disposed at an incline with respect to the source of solar radiations, and a pliable transparent plastic film overlying the backing plate. Water is introduced at the top of the backing plate between it and the transparent plastic film and flows downwardly by gravity in the form of a thin uniform layer, the solar radiations passing through the transparent film and the water layer and being absorbed by the darkened backing plate. Such solar collectors are primarily intended for applications wherein a relatively large volume of water is to be heated to a small temperature rise, e.g. for heating swimming pools, cisterns, tanks and the like. An example of such a solar heater is described in U.S. Pat. No. 3,146,774.